Advanced Silicon Etch
Encyclopedia
Advanced Silicon Etch is a deep reactive ion etching (DRIE) technique to rapidly etch deep and high aspect ratio structures in silicon.
ASE was pioneered by Surface Technology Systems Plc. (STS
) in 1994 in the UK. STS has continued to develop this process with even greater etch rates while maintaining side wall roughness and selectivity.
STS developed the switched process originally invented by Dr. Larmer at Bosch, Stuttgart.
ASE consists in combining the fast etch rates achieved in an isotropic Si etch (usually making use of an SF6 plasma
) with a deposition or passivation
process (usually utilising a C4F8
plasma condensation process) by alternating the two process steps.
This approach achieves the fastest etch rates whilst maintaining the ability to etch anisotropically
, typically vertically in Microelectromechanical Systems (MEMS
) applications.
Surface Technology Systems
ASE was pioneered by Surface Technology Systems Plc. (STS
STS
-Science, medicine, meteorology and technology:*Science and technology studies*Superior temporal sulcus*Socio-technical systems*Severe tropical storm*Scanning tunneling spectroscopy, a spectroscopy technique based on Scanning Tunneling Microscopy...
) in 1994 in the UK. STS has continued to develop this process with even greater etch rates while maintaining side wall roughness and selectivity.
STS developed the switched process originally invented by Dr. Larmer at Bosch, Stuttgart.
ASE consists in combining the fast etch rates achieved in an isotropic Si etch (usually making use of an SF6 plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
) with a deposition or passivation
Passivation
Passivation is the process of making a material "passive", and thus less reactive with surrounding air, water, or other gases or liquids. The goal is to inhibit corrosion, whether for structural or cosmetic reasons. Passivation of metals is usually achieved by the deposition of a layer of oxide...
process (usually utilising a C4F8
Octafluorocyclobutane
Octafluorocyclobutane, or perfluorocyclobutane, C4F8, is an organofluorine compound which enjoys several niche applications. It is related to cyclobutane by replacement of all C-H bonds with C-F bonds...
plasma condensation process) by alternating the two process steps.
This approach achieves the fastest etch rates whilst maintaining the ability to etch anisotropically
Anisotropy
Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies identical properties in all directions. It can be defined as a difference, when measured along different axes, in a material's physical or mechanical properties An example of anisotropy is the light...
, typically vertically in Microelectromechanical Systems (MEMS
Microelectromechanical systems
Microelectromechanical systems is the technology of very small mechanical devices driven by electricity; it merges at the nano-scale into nanoelectromechanical systems and nanotechnology...
) applications.
"The ASE HRM is an evolution of the previous generations of ICPICP-Business:* International Comfort Products Corporation, a company that manufactures and markets central air conditioning systems, gas and oil furnaces* Indonesian Crude Price...
design, now incorporating a decoupled plasma source (patent pending). This decoupled source generates very high density plasma which is allowed to diffuse into a separate process chamber. Through careful chamber design, the excess ions that are detrimental to process control are reduced, leaving a uniform distribution of fluorineFluorineFluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
free-radicals at a higher density than that available from the conventional ICPICP-Business:* International Comfort Products Corporation, a company that manufactures and markets central air conditioning systems, gas and oil furnaces* Indonesian Crude Price...
sources. The higher fluorine free-radical density facilitates increased etch rates, typically over three times the etch rates achieved with the original Bosch process. Also, as a result of the reduction in the effect of localised depletion of these species, improved uniformity for many applications can be achieved."
Further reading
Publications on this subject can be read atSurface Technology Systems